Measuring your heart rate, known as beats per minute, is usually a simple process that indicates cardiovascular performance. However, heart rhythm irregularities, particularly those caused by Premature Ventricular Contractions (PVCs), introduce a significant complication. When the heart’s rhythm is irregular, standard methods of quickly checking a pulse become unreliable, making it difficult to get an accurate reading. Understanding how PVCs disrupt the normal pulse wave is the first step toward accurately monitoring your heart rate.
What Are Premature Ventricular Contractions?
Premature Ventricular Contractions are extra heartbeats that originate in the ventricles, the lower pumping chambers of the heart. These premature beats occur earlier than the next expected normal heartbeat, temporarily disrupting the regular rhythm. Because the beat happens so early, the ventricles do not have enough time to fully fill with blood before contracting, resulting in a contraction that is often less effective at pushing blood out to the body.
The mechanical result of this weak contraction is that the pulse wave traveling to peripheral arteries, such as those in the wrist or neck, is diminished or absent. Following the premature beat, there is a pause, known as a compensatory pause, before the next normal beat. This subsequent beat often feels stronger because the heart has had extra time to fill with blood, leading to the sensation of a “skipped” beat followed by a “thump.”
Why Standard Counting Methods Fail
The physiological impact of the weak PVC-induced contraction causes standard, short-interval heart rate counting methods to fail. When counting a pulse, people often use a 15-second interval and multiply the count by four to determine the beats per minute. This method relies on the assumption of a steady, regular rhythm, which an irregular rhythm violates.
If a PVC occurs during the short counting window, the weak pulse wave it generates may not be palpable at the wrist or neck, even though the heart muscle electrically contracted. This difference between the actual number of heartbeats and the number of felt pulse waves is called a pulse deficit. Missing a beat during a short count means the final calculated heart rate will be artificially lower than the true electrical heart rate. This inaccuracy can be significant, especially if PVCs are frequent.
Manual Techniques for Accurate Heart Rate
To obtain an accurate heart rate when PVCs are present, count the pulse for a full 60 seconds. This extended counting period ensures that any skipped or weak beats are accounted for within the overall minute, providing a representative average of the heart’s activity. The technique involves locating a reliable pulse point, such as the radial artery on the wrist or the carotid artery on the neck.
Use the index and middle fingers to apply gentle pressure until the pulsation is clearly felt. Start the count at zero precisely when a 60-second timer begins. Focus on feeling every distinct pulse wave, even those that feel weaker or slightly different than the others. The final number of pulse waves felt after 60 seconds is the most accurate manual heart rate in beats per minute.
When Digital Monitors Miscalculate
Digital devices, such as smartwatches, fitness trackers, and automatic blood pressure cuffs, often struggle to provide accurate readings for irregular rhythms. Many of these devices use optical sensors, known as photoplethysmography (PPG), which measure heart rate by detecting changes in blood volume in the microvasculature. This technology assumes a consistent and strong pulsatile blood flow.
When a PVC occurs, the resulting weak contraction leads to a diminished blood volume change at the periphery, which the PPG sensor may fail to register as a beat. This often results in a falsely low heart rate reading on the device, similar to the error in the manual short-interval count. Other devices, like chest strap monitors, rely on electrical impulses and may count the PVC as a full beat, sometimes leading to an artificially high or erratic reading. If a digital monitor displays an erratic or unusually low reading, the most dependable step is to revert to the manual 60-second counting technique.